Characterization of Mechanical, Thermal, and Electrical Properties of Carbon Fiber Polymer Composites by Modeling

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In this paper, the mechanical, thermal and electrical properties of carbon fiber modified thermoplastic polyimide were numerically analyzed by finite element analysis. A three-dimensional model was created, in which continuous carbon fibers are aligning and paralleling to each other and uniformly distributing in the polymer matrix. The behaviors of the composites in two extreme situations, i.e., parallel or perpendicular to carbon fiber direction, were simulated. The effects of the volume fraction of carbon fiber content on the physical properties were investigated. It shows clearly that carbon fibers significantly improve the mechanical strength, and thermal and electrical conductivities. The future work includes investigation of the physical properties of the conductive network of the composites with random carbon fiber orientation, and different fillers, such as graphite, and carbon nanotubes.

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Characterization of Mechanical, Thermal, and Electrical Properties of Carbon Fiber Polymer Composites by Modeling

  1. 1. 2013 American Transactions on Engineering & Applied Sciences. American Transactions on Engineering & Applied Sciences http://TuEngr.com/ATEAS Characterization of Mechanical, Thermal, and Electrical Properties of Carbon Fiber Polymer Composites by Modeling Zhong Hu a*, Xingzhong Yan b, James Wu c, and Michelle Manzo c a Department of Mechanical Engineering, South Dakota State University, USA Department of Electrical Engineering &Computer Science, South Dakota State University, USA c Electrochemistry Branch, NASA Glenn Research Center, USA b ARTICLEINFO A B S T RA C T Article history: Received February 06, 2013 Received in revised form March 06, 2013 Accepted March 08, 2013 Available online March 11, 2013 In this paper, the mechanical, thermal and electrical properties of carbon fiber modified thermoplastic polyimide were numerically analyzed by finite element analysis. A three-dimensional model was created, in which continuous carbon fibers are aligning and paralleling to each other and uniformly distributing in the polymer matrix. The behaviors of the composites in two extreme situations, i.e., parallel or perpendicular to carbon fiber direction, were simulated. The effects of the volume fraction of carbon fiber content on the physical properties were investigated. It shows clearly that carbon fibers significantly improve the mechanical strength, and thermal and electrical conductivities. The future work includes investigation of the physical properties of the conductive network of the composites with random carbon fiber orientation, and different fillers, such as graphite, and carbon nanotubes. Keywords: Carbon Fibers Polymer Composites Physical Properties Characterization Finite Element Analysis 2013 American Transactions on Engineering & Applied Sciences. *Corresponding author (Z. Hu). Tel/Fax: +1-605-688-4817/+1-605-688-5878. E-mail address: Zhong.Hu@sdstate.edu. 2013. American Transactions on Engineering & Applied Sciences. Volume 2 No. 2 ISSN 2229-1652 eISSN 2229-1660 Online Available at http://TuEngr.com/ATEAS/V02/133-148.pdf 133
  2. 2. 1. Introduction Polymers are lightweight, flexible, resistant to heat and chemicals, and non-conductive and transparent to electromagnetic radiation. Therefore, they are used in the electronics industry for flexible cables, as an insulating film, and for medical tubing. Thus, they are not suitable for use as enclosures for electronic equipment because they cannot shield it from outside radiation. Also they cannot prevent the escape of radiation from the component. (Elimat et al. 2010; Navin and Deepak 2004) Several fillers can be added to the insulating polymeric matrix in order to achieve different conductivity ranges for a variety of industrial applications. (Delmonte 1990; Neelakanta 1995) Polyacrylonitrile (PAN)-based carbon fibers (CFs) possess high stiffness and strength, low expansion coefficient, and elevated thermal and electric conductivity measured along the fiber direction. (Lei et al. 2008; Donnet et al. 1990; Park and Chou 2000; Chand 2000) Carbon fiber (CF)/polymer composites are used in the aerospace industry on account of their high-specific stiffness and strength, which are higher than in metallic materials. (Surendra et al. 2009) Conducting polymers have been extensively studied because of their potential applications in light-emitting devices, batteries, electromagnetic shield, and other functional applications. (Anupama et al. 2010; Tsotra and Friedrich 2003; Tse et al. 1981) The ability of these composites to serve as capacitors and other circuit element means that the structures is itself the electronics, so that the electronics 'vanish' into the structure. (Luo and Chung 2001) In the case of continuous CF polymer-matrix composites, CFs are the conductors (resistors) and they can be intercalated to become electron metals or hole metals. (Chung and Wang 1999) By having the electronics vanish into the structure, space is saved. The space saving is particularly valuable for capacitors of large capacitance in space applications. In addition to space saving, structural electronics have the advantage of being mechanically rugged and inexpensive, since structural materials are necessarily rugged and inexpensive. The use of a structure as a capacitor is particularly valuable in conjunction with structures that are powered by solar cells, as the structure (capacitor) can be used to store the electrical energy generated by the solar cells. (Luo and Chung 2001; Chung and Wang 1999; Zhu et al. 2011; Stoller and Ruoff 2010). In this paper, the mechanical, thermal and electrical properties of CF modified polyimide (PI) matrix composite will be numerically analyzed by finite element analysis (FEA). (Herakovich 1998; Minus and Kumar 2007; Fei et al. 2007) A three-dimensional model will be created, in 134 Zhong Hu, Xinghong Yan, James Wu, and Michelle Manzo
  3. 3. which continuous CFs will be aligning and paralleling to each other and uniformly distributing in the matrix. The behaviors of the composite in two extreme situations, i.e., parallel or perpendicular to the CF direction, will be simulated. The effects of CF volumetric fraction on the physical (mechanical, thermal, and electrical) properties will be investigated. 2. Modeling by Finite Element Analysis Although the material properties for the composite are anisotropic, for each component (CF filler or polymer matrix) they could be treated as isotropic. Assuming that each set of properties (mechanical, thermal, or electrical properties) is independent. Therefore, each set of the properties can be evaluated separately. For mechanical properties, a linear and elastic stress-strain relationship is assumed. Therefore, for each element of one kind material (CF filler or polymer matrix), the structural governing equation is (ANSYS Inc. 2012) (1) where is the stress vector, is the elastic strain vector, and is the elastic stiffness matrix. For thermal properties, the heat transfer governing equation of conduction at steady-state is 0 where is the heat flux vector, (2) is the vector operator, T is temperature, and is the thermal conductivity matrix. For electrical properties, the electromagnetic field governing equations are matrix. For electrical properties, the electromagnetic field governing equations are ; where is curl operator, ; · is divergence operator, is the total current density vector, electric field intensity vector, · 0; · (3) is the magnetic field intensity vector, is the electric flux density vector, t is time, is the is the magnetic flux density vector, and ρe is the electric charge density. Therefore, each element formulations can be developed and the equations for each element can *Corresponding author (Z. Hu). Tel/Fax: +1-605-688-4817/+1-605-688-5878. E-mail address: Zhong.Hu@sdstate.edu. 2013. American Transactions on Engineering & Applied Sciences. Volume 2 No. 2 ISSN 2229-1652 eISSN 2229-1660 Online Available at http://TuEngr.com/ATEAS/V02/133-148.pdf 135
  4. 4. be assembled into global matrix for the entire domain of the composite (including both CF filler and polymer matrix). In this work, a commercial FEA software ANSYS was used. A three-dimensional element SOLID223, i.e., a 3-D 20-node high-order accuracy coupled–field (structural, thermal, and electrical) solid element was adopted. The isotropic properties of each material component were assumed. PAN-based carbon fibers with filament size of 5μm in diameter are chosen as polymeric matrix filler and polyimides as polymeric matrix. The physical properties of both materials are listed in Table 1. (Herakovich 1998; Minus and Kumar 2007; Fei at al. 2007; Ayish and Zihlif 2010; Dupont Kapton 2010). Table 1: Physical properties of polyimide film and carbon fibers. Modulus Thermal Thermal Specific Electrical of Poisson Density Expansion Dielectric Conductivity Heat Resistivity Materials Elasticity Ratio (kg/m3) Coefficient Constant (W/m⋅K) (J/kg⋅K) (Ω⋅m) -6 (GPa) (10 /K) Polyimide 2.5 0.34 1,420 17 0.10 1,090 1.5×1015 3.4 Film Carbon 2000 310 0.2 1,800 0.5 12 965 0.15×10-4 Fibers The three-dimensional solid model is shown in Figure 1, in which the cylindrical components represent CFs and the cubic volume is the polymeric matrix, and z-axis represents the CF orientation and x-y plane is perpendicular to the CF orientation. The dimensions of the solid model are represented by L (length in x-axis) × W (width in y-axis) × H (height in z-axis). The FEA meshes are shown in Figure 2. The dimensions of the model in the simulations, in terms of CF volumetric fraction, are listed in Table 2. Figure 1: 3-D solid model of the composite. 136 Figure 2: 3-D FEA meshes of the composite. Zhong Hu, Xinghong Yan, James Wu, and Michelle Manzo
  5. 5. For modeling the modulus of elasticity in z-axial direction (CF direction), the uniaxial tensile testing along z-axial direction is conducted, in which the bottom face (z=0) is fixed and the top face (z=H) is pulled 0.1% (within elastic deformation region) in +z-axial direction (i.e., z-axial strain εz=0.001). For symmetric purpose, the displacement in x-axial direction on the face of x=0 is constrained (ux=0 on the face of x=0), and the displacement in y-axial direction on the face of y=0 is also constrained (uy=0 on the face of y=0). The z-axial forces on the top face (z=H) are accumulated as Fz, so that the average stress in z-axial direction, σz, can be calculated. The modulus of elasticity in z-axial (CF) direction, E1, is calculated. Table 2: The dimensions of the model in terms of CF volumetric fraction. CF Volume Fraction CF Diameter Length (x-axis) Width (y-axis) Height (z-axis) (%) (μm) (μm) (μm) (μm) 10 20 30 40 50 5 5 5 5 5 84.07 59.45 48.54 42.04 37.60 56.05 39.63 32.36 38.02 25.07 28.02 18.82 16.18 14.01 12.53 Figure 3: Displacement ux under z-axial tension Figure 4: Displacement uy under z-axial (εz=0.001). tension (εz=0.001). (4) Poisson ratio in x-axis (ν12) or y-axis (ν13) under this uniaxial tensile test can also be calculated ; *Corresponding author (Z. Hu). Tel/Fax: +1-605-688-4817/+1-605-688-5878. E-mail address: Zhong.Hu@sdstate.edu. 2013. American Transactions on Engineering & Applied Sciences. Volume 2 No. 2 ISSN 2229-1652 eISSN 2229-1660 Online Available at http://TuEngr.com/ATEAS/V02/133-148.pdf (5) 137
  6. 6. where the average strain in x-axial and y-axial directions, εx and εy, are calculated as (as shown in Figures 3 and 4) (on face) (6) (on face) (7) For modeling the modulus of elasticity in x-axial direction, E2, (perpendicular to CF direction), the uniaxial tensile testing along x-axial direction is conducted. The corresponding boundary conditions are applied, i.e., the left-front face (x=0) is fixed and the right-back face (x=L) is pulled 0.1% (within elastic deformation region) in +x-axial direction (i.e., x-axial strain εx=0.001). For symmetric purpose, the displacement in y-axial direction on the face of y=0 is constrained (uy=0 on the face of y=0), and the displacement in z-axial direction on the face of z=0 is also constrained (uz=0 on the face of z=0). The similar calculation steps can be adopted for calculating the average stress and strain, σx and εy, Modulus of elasticity E2, and Poisson ratio ν23, as shown in Figures 5 and 6, ; (8) Figure 5: Displacement ux under x-axial tension (εx=0.001). Figure 6: Displacement uy under x-axial tension (εz=0.001). For modeling the thermal conductivity in z-axial direction (CF direction), the bottom face (z=0) is assigned with temperature of 20°C and the top face (z=H) is assigned with temperature of 21°C (1°C difference between two faces). The equivalent thermal conductivity in z-axial direction, 138 Zhong Hu, Xinghong Yan, James Wu, and Michelle Manzo
  7. 7. k1, is calculated as ( ) (on face) (9) where qz is the heat flux in z-axial direction, and (Tz=H - Tz=0) is the temperature difference between bottom face and top face. The similar steps can be adopted for calculating the equivalent thermal conductivity in x-axial direction (perpendicular to CF direction), k2, as shown in Figures 7 and 8. Figure 7: Heat flux (W/m2) vector distribution under temperature difference (1°C) in z-direction. Figure 8: Heat flux (W/m2) vector distribution under temperature difference (1°C) in x-direction. Similar to the thermal conductivity calculation, for modeling the electrical conductivity in z-axial direction (CF direction), the bottom face (z=0) is assigned with voltage of 0 volt and the top face (z=H) is assigned with voltage of 0.1 volt. The equivalent electrical conductivity in z-axial direction, κ1, is calculated as ( ) (on face) (10) where iz is the current density in z-axial direction, and (Vz=H–Vz=0) is the voltage difference between bottom face and top face. The similar steps can be adopted for calculating the equivalent electrical conductivity in x-axial direction (perpendicular to CF direction), κ2. *Corresponding author (Z. Hu). Tel/Fax: +1-605-688-4817/+1-605-688-5878. E-mail address: Zhong.Hu@sdstate.edu. 2013. American Transactions on Engineering & Applied Sciences. Volume 2 No. 2 ISSN 2229-1652 eISSN 2229-1660 Online Available at http://TuEngr.com/ATEAS/V02/133-148.pdf 139
  8. 8. Figure 9: Displacement uz under z-axial tension (εz=0.001). Figure 10: Stress σz (MPa) under z-axial tension (εz=0.001). Figure 11: Strain εx under x-axial tension (εx=0.001, 10%CF). Figure 12: Strain εx under x-axial tension (εx=0.001, 50%CF). Figure 13: Stress σx (MPa) under x-axial tension (εx=0.001, 10%CF). Figure 14: Stress σx (MPa) under x-axial tension (εx=0.001, 50%CF). 3. Results and Discussion The effects of CF volume fraction on the physical properties of the composite are investigated. Figure 9 shows z-axial displacement under z-axial tension, which gives a uniform distribution of the displacement. Therefore, the strain in z-axial is constant throughout the entire domain. Figure 140 Zhong Hu, Xinghong Yan, James Wu, and Michelle Manzo
  9. 9. 10 shows z-axial stress under z-axial tension. It shows clearly that the major load applied is taken by CFs due to their much higher stiffness. These two figures are useful for analyzing modulus of elasticity, E1, in CF direction. Figures 11-14 show x-axial strain and stress distribution under x-axial tension for 10%CF and 50%CF, respectively. It can be seen that the more the CF%, the worse the uniformity of the distributions and the more the contribution from CFs. These four figures are useful for analyzing modulus of elasticity, E2, in perpendicular to CF direction. Figures 15 and 16 show the moduli of elasticity, E1 (in CF direction) and E2 (perpendicular to CF direction). It clearly shows that the modulus of elasticity measured in CF direction is linearly increasing as CF% increasing, and the magnitude is primarily dominated by CF part due to its much higher stiffness. It also shows a nonlinear increasing of the modulus of elasticity in perpendicular to CF direction as CF% increasing due to the cross-section interaction increasing as mentioned in Figures 11-14. However, the magnitude is primarily dominated by polymer matrix due to the discontinuity of CFs in the plane, therefore, the load has been transferred primarily within polymer matrix, the softer component. In CF direction, the modulus of elasticity is much 1.6E+5 Modulus of Elasticity E2(MPa) Modulus of Elasticity E1 (MPa) higher than that in perpendicular to the CF direction. 1.4E+5 E1 in CF direction 1.2E+5 1.0E+5 8.0E+4 6.0E+4 4.0E+4 2.0E+4 0.0E+0 0 0.1 0.2 0.3 0.4 CF Volume Fraction Figure 15: Modulus of elasticity, E1, in CF direction. 0.5 8E+3 7E+3 E2 perpendicular to CF direction 6E+3 5E+3 4E+3 3E+3 2E+3 0 0.1 0.2 0.3 CF Volume Fraction 0.4 Figure 16: Modulus of elasticity, E2, perpendicular to CF direction. Figures 17-20 show the strain distributions in the cross-section perpendicular to CF direction under z-axial tension for evaluating Poisson ratios of υ12 and υ13. It clearly shows that the more the CF%, the worse the uniformity of the strain distribution is and the more the contribution by CF component. Furthermore, the strain distribution in x-axial is symmetric to that in y-axial due to the model symmetry in x-axis and y-axis. *Corresponding author (Z. Hu). Tel/Fax: +1-605-688-4817/+1-605-688-5878. E-mail address: Zhong.Hu@sdstate.edu. 2013. American Transactions on Engineering & Applied Sciences. Volume 2 No. 2 ISSN 2229-1652 eISSN 2229-1660 Online Available at http://TuEngr.com/ATEAS/V02/133-148.pdf 141 0.5
  10. 10. Figures 21-22 show y-axial strain distribution in the cross-section perpendicular to CF direction under x-axial tension for evaluating Poisson ratio of υ23. It clearly shows again that the more the CF%, the worse the uniformity of the strain distribution is the more the contribution from CF component to the deformation. Figure 17: Strain εx under z-axial tension (εz=0.001, 10%CF). Figure 18: Strain εx under z-axial tension (εz=0.001, 50%CF). Figure 19: Strain εy under z-axial tension (εz=0.001, 10%CF). Figure 20: Strain εy under z-axial tension (εz=0.001, 50%CF). Figure 21: Strain εy under x-axial tension (εx=0.001, 10%CF). Figure 22: Strain εy under x-axial tension (εx=0.001, 50%CF). 142 Zhong Hu, Xinghong Yan, James Wu, and Michelle Manzo
  11. 11. Figure 23 shows the Poisson ratios of the composites. υ12 and υ13 are the same due to their symmetry in model. Furthermore, υ12 and υ13 are almost linearly decreasing as CF% increasing, starting from 0.34 of the polymer matrix’s Poisson ratio (0% CF). υ23 is nonlinearly decreasing and decreasing from slower to faster as CF% increasing, starting from the same value. 0.34 Poisson Ratio 0.32 0.30 υ12 0.28 υ13 0.26 υ23 0.24 0.22 0.20 0 0.1 0.2 0.3 0.4 0.5 CF Volume Fraction Figure 23: Poisson ratios of the composites. Thermal and electrical properties have the similar trends as the moduli of elasticity. Figures 24-25 show the thermal and electrical conductivities, k1 and κ1, in CF direction, respectively. 7 3.5E+4 Equivalent Electrical Conductivity κ1 (S/m) Equivalent Thermal Conductivity k1(W/mK) Again, CFs play the major role in these properties due to their much higher conductivities. 6 3.0E+4 k1 in CF direction 5 κ1 in CF direction 2.5E+4 4 2.0E+4 3 1.5E+4 2 1.0E+4 1 5.0E+3 0 0.0E+0 0 0.1 0.2 0.3 0.4 CF Volume Fraction Figure 24: Thermal conductivity, k1, in CF direction. 0.5 0 0.1 0.2 0.3 0.4 0.5 CF Volume Fraction Figure 25: Electric conductivity, κ1, in CF direction. *Corresponding author (Z. Hu). Tel/Fax: +1-605-688-4817/+1-605-688-5878. E-mail address: Zhong.Hu@sdstate.edu. 2013. American Transactions on Engineering & Applied Sciences. Volume 2 No. 2 ISSN 2229-1652 eISSN 2229-1660 Online Available at http://TuEngr.com/ATEAS/V02/133-148.pdf 143
  12. 12. Figures 26 and 27 show the heat flux vector distributions under temperature difference in x-axial direction for 10% CF and 50%CF, respectively. Similarly, Figures 28 and 29 show the electrical field vector distributions under voltage difference in x-axial direction for 10%CF and 50%CF, respectively. Again, the more the CF%, the worse the uniformity of the distributions is. Figure 26: Heat flux (W/m2) vector distribution under temperature difference (1°C) in x-direction (10%CF). Figure 27: Heat flux (W/m2) vector distribution under temperature difference (1°C) in x-direction (50%CF). Figure 28: Electric field (V/μm) vector distribution under voltage difference (0.1V) in x-direction (10%CF). Figure 29: Electric field (V/μm) vector distribution under voltage difference (0.1V) in x-direction (50%CF). Figure 30 shows the thermal conductivities, k2, in perpendicular to CF direction. The modeling results are compared with the experimental data from reference (Fei et al. 2007). Both results are showing the nonlinearity, and the conductivities are both nonlinearly increasing as CF% increasing. The experimental data are lower than that by modeling, because the uniformity and bonding condition (cavities existing) in the reality are getting worse as %CF increasing which lowered the heat transfer rate. In contrast, in the modeling a perfect CF distribution and bonding 144 Zhong Hu, Xinghong Yan, James Wu, and Michelle Manzo
  13. 13. between the matrix and the filler are always assumed. Comparing Figure 30 with Figure 24, it can be seen that the thermal conductivity in CF direction is about one order higher than that in perpendicular directions due to the difference of the thermal conductivities between these two components. Figure 31 shows the electric conductivities, κ2, in perpendicular to CF direction, showing the nonlinearity again. Comparing Figure 31 with Figure 25, it can be seen that the electric conductivity in CF direction is about 19 orders higher than that in perpendicular to CF direction. Because CFs are perfect conductor material, so even though 10% volume of CFs could perform very well conduction if CFs could be well aligned and keep continuity in the conduction direction. In contrast, the electric conductivity in perpendicular to CF direction is almost zero, due to the perfect insulator behavior of the polymer and discontinuity of CFs, which could be treated as an open circuit. 2.5 Equivalent Electrical Conductivity κ2 ×10-15 (S/m) 0.40 Equivalent Thermal Conductivity k2 (W/mK) k2 perpendicular to CF direction k2 from experimental data (Lei et al. 2007) 0.35 0.30 0.25 0.20 0.15 0.10 κ2 perpendicular to CF direction 2.0 1.5 1.0 0.5 0 0.1 0.2 0.3 0.4 0.5 CF Volume Fraction Figure 30: Thermal conductivity, k2, in perpendicular to CF direction. 0.6 0 0.1 0.2 0.3 0.4 0.5 CF Volume Fraction Figure 31: Electric conductivity, κ2, perpendicular to CF direction. 4. Conclusion Mechanical, thermal, and electrical properties of a carbon fiber modified polymeric matrix composite have been numerically investigated by finite element modeling. A three-dimensional model has been created, in which continuous CFs were aligned and parallel to each other and uniformly distributed in the polymer matrix. The behaviors of the composite in two extreme situations, i.e., parallel or perpendicular to carbon fiber direction, have been analyzed. The effects *Corresponding author (Z. Hu). Tel/Fax: +1-605-688-4817/+1-605-688-5878. E-mail address: Zhong.Hu@sdstate.edu. 2013. American Transactions on Engineering & Applied Sciences. Volume 2 No. 2 ISSN 2229-1652 eISSN 2229-1660 Online Available at http://TuEngr.com/ATEAS/V02/133-148.pdf 145
  14. 14. of the CF volume fraction on these physical properties have been investigated. It shows clearly that CFs significantly improve the mechanical strength, thermal and electrical conductivity in CF direction, these physical properties of the composites are primarily dominated by CF volume fraction, and are linearly increasing as the CF volume fraction increasing, due to the much higher performance of the CFs. The physical properties in perpendicular to CF direction are nonlinearly increasing as the CF volume fraction increasing, but the absolute values are still very low due to the low performance of the polymer matrix. The future work should expand this modeling technique to look into the other physical properties, the physical properties of the conductive network of the composites with random CF orientation, different distribution of the filler, different CF length, different fillers, such as graphite, and carbon nanotubes, and different cross-section of the fillers, the role of interfacial interaction between the matrix and the filler, etc. 5. Acknowledgements This work was supported by NASA EPSCoR Funds #NNX07AL04A, the State of South Dakota, Mechanical Engineering Department and the College of Engineering at South Dakota State University. 6. References ANSYS Theory Reference Manual, ANSYS version 13.0, ANSYS Inc., 2012. Anupama K, Paramjit S, Jyot I. (2010). Mechanical and electrical conductivity study on epoxy/graphite composites, J. Reinf. Plast. Compos., 29, 1038-1044. Ayish IO, Zihlif AM. (2010). Electrical properties of conductive network in carbon fibers/polymer composites, Journal of Reinforced Plastics & Composites, 29(21), 3237-3243. Chand S. (2000). Review carbon fibers for composites, J. Mater. Sci., 35, 1303-1313. Chung DDL, Wang S. (1999). Carbon fiber polymer-matrix structural composite as a semiconductor and concept of optoelectronic and electronic devices made from it, Smart Mater. Struct., 8, 161-166. Delmonte J. (1990). Metal/Polymer Composites, Van Nostrand Reinhold, New York. 146 Zhong Hu, Xinghong Yan, James Wu, and Michelle Manzo
  15. 15. Donnet JB, Bansal RC, Wang MJ. (1990). Carbon Fibers, 3rd ed. Dekker, New York. Dupont Kapton Polyimide Film General Specifications, Bulletin GS-96-7, June 2010. Elimat ZM, Hamideen MS, Schulte KI, Wittich H, de la Vega A, Wichmann M, Buschhorn S. (2010). Dielectric properties of epoxy/short carbon fiber composites, J. Mater. Sci., 45, 5196-5203. Fei HY, Zhu P, Song YJ, Gu HP, Wang XD, Huang P. (2007). Thermal conduction of thermoplastic polyimide composites modified with graphite/carbon fiber, Acta Materiae Compositae Sinica, 24 (5), 44-49. Herakovich CT. (1998). Mechanics of Fibrous Composites, John Wiley & Sons, Inc., New York, NY, USA. Lei L, Yiping T, Haijun Z, Jianhua Z, Wenbin H. (2008). Fabrication and properties of short carbon fibers reinforced copper matrix composites, J. Mater. Sci., 43, 974-979. Luo X-C, Chung DDL. (2001). Carbon-fiber/polymer-matrix composites as capacitors, Composites Science and Technology, 61, 885-888. Minus ML, Kumar S. (2007). Carbon Fibers, Kirk-Othmer Encyclopedia of Chemical Technology, vol.26, John Wiley & Sons, Inc., New York, USA. Navin C, Deepak J. (2004). Evaluation of a.c. conductivity behaviour of graphite filled polysulphide modified epoxy composites, Bull. Mater. Sci., 27, 227-233. Neelakanta PS. (1995) Handbook of Electromagnetic Materials, CRC Press, Boca Raton. Park SJ, Chou MS. (2000). Effect of anti-oxidative filler on the interfacial mechanical properties of carbon–carbon composites measured at high temperature, Carbon, 38(7), 1053-1058. Stoller MD, Ruoff RS. (2010). Methods and best practices for determining an electrode material’s performance for ultracapacitors, Energy and the Environment, 3, 1294-1301. Surendra K, Neeti S, Ray BC. (2009). Microstructural and mechanical aspects of carbon/epoxy composites at liquid, J. Reinf. Plast. Compos., 28(16), 2013-2023. Tse KW, Moyer CA, Arajs S. (1981). Electrical conductivity of graphite fiber-epoxy resin composites, Mater. Sci. Eng., 49, 41-46. Tsotra P, Friedrich S. (2003). Electrical and mechanical properties of functionally graded epoxy-resin/carbon fibre composites, Compos. A. Appl. Sci. Manuf., 34, 75-82. *Corresponding author (Z. Hu). Tel/Fax: +1-605-688-4817/+1-605-688-5878. E-mail address: Zhong.Hu@sdstate.edu. 2013. American Transactions on Engineering & Applied Sciences. Volume 2 No. 2 ISSN 2229-1652 eISSN 2229-1660 Online Available at http://TuEngr.com/ATEAS/V02/133-148.pdf 147
  16. 16. Zhu YW, Murali S, Stoller MD, Ganesh K J, Cai WW, Ferreira PJ, Pirkle A, Wallance RM, Cychosz KA, Thommes M, Su D, Stach EA, Ruoff RS. (2011). Carbon-based supercapacitors produced by activation of graphene, Science, 332, 1537-1541. Dr. Zhong Hu is an Associate Professor of Mechanical Engineering at South Dakota State University. He received his BS and Ph.D. in Mechanical Engineering from Tsinghua University. He has worked for railway manufacturing industry as a senior engineer, Tsinghua University as a professor, Japan National Laboratory as a fellow, Cornell University, Penn State University and Southern Methodist University as a research associate. He has authored over 80 peer-reviewed publications in the journals, proceedings and book chapters in the areas of nanotechnology and nanoscale modeling by quantum mechanical/molecular dynamics (QM/MD); development of renewable energy related materials; mechanical strength evaluation and failure prediction by finite element analysis (FEA) and nondestructive engineering (NDE); design and optimization of advanced materials (such as biomaterials, carbon nanotube, polymer and composites). Dr. Xingzhong Yan is an assistant Professor of Electrical Engineering & Computer Science at South Dakota State University. He received his BSc in Chemistry from Hunan Normal University, MSc in Physical Chemistry from Chinese Academy of Science, and Ph.D. in Polymer Chemistry and Physics from Sun Yat-sen University. He has published over 60 peer-reviewed papers in journals, proceedings, and book chapters in the areas of solar cells, optical materials, femtosecond spectroscopy, light and thermal management, optical sensors and electrical storage. Dr. James Jianjun Wu joined the Electrochemistry branch of NASA in 2010. He earned his Ph.D. in Chemistry from the University of Illinois at Urbana-Champaign and his Masters degree in Chemistry/Analytical Chemistry from Rutgers University at New Brunswick, NJ. He holds another Masters degree in Electrochemistry/Electroanalytical Chemistry, and a BS degree in Chemistry/Chemical Engineering. Dr. Wu possesses postdoctoral experience and more than 10 years of industrial R&D experience prior to joining NASA. Dr. Wu has a varied experience base with the research and development of catalysts, advanced energy storage materials and electrochemical systems, Michelle Manzo has served as Chief of the Electrochemistry Branch since 2005. In this role she oversees the development of electrochemical systems for future NASA missions. She has been involved in the development of batteries and fuel cells with an emphasis on aerospace batteries. She began with the development of alkaline batteries, specifically nickel-hydrogen, nickel-cadmium, silver-zinc and nickel-zinc and more has recently been addressing lithium-based systems. Michelle has been involved with interagency aerospace flight battery systems collaborations. Michelle has received numerous awards and recognition throughout her career. She has authored or co-authored more than 40 papers and has been recognized with various awards that include a NASA Exceptional Achievement Medal, a NASA Exceptional Service Medal, an R&D 100 award, and NASA Group Achievement Awards for the Li-Ion Battery Technology Team and the NASA Spacecraft Fuel Cell Development Team. Peer Review: This article has been internationally peer-reviewed and accepted for publication according to the guidelines given at the journal’s website. 148 Zhong Hu, Xinghong Yan, James Wu, and Michelle Manzo

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